Abstract: An apparatus for and a method of measuring material thickness with magnetics. The thickness monitoring system includes a thickness monitor, a probe, and a target. In a preferred embodiment, the probe is positioned on one side of an article for which the thickness is to be determined. The target is positioned on the opposite side of the article from the probe. The probe includes an excitation coil, a field compensation coil, and a magnetic sensor. The method includes energizing the excitation coil to excite a response from the target, compensating for the effect of the excitation coil on the magnetic sensor, measuring the response of the target with the magnetic sensor, and determining the thickness of the article from the measured response. The preferred mode of energizing the excitation coil is with an AC waveform; however DC, multi-frequency AC, or a combination of AC and DC waveforms may be used.

Abstract: Methods are disclosed for non-invasive screening of the human body by rejecting the magnetic response from biological tissues in the region of interest and outputting data corresponding to the magnetic response of a ferromagnetic foreign body within the region of interest.

Abstract: An apparatus for and a method of single-sided MRI with a palm-sized probe. The probe includes a planar permanent magnet having a gap between the north and south poles of the magnet. Positioned in the gap are an RF coil and a pair of gradient coils. The gradient coils are located on either side of the RF coil. The probe further includes an RF tuning circuit and a gradient input. In use, the pair of gradient coils produce a controlled magnetic field gradient over the field of view thereby improving image resolution.

Abstract: A probe instrument using room-temperature sensor(s) that can measure magnetic susceptibilities variations. The instrument includes room temperature magnetic sensors, and detects the sample, that is the tissue response to an applied field coil. The sensors that can be used include magnetoresistive, fluxgate and magnetoinductive sensors. The applied field coil dimensions are chosen so that the applied field is optimized for maximum response from the item of interest while minimizing the effects due to the overlying tissue and at the same time not unduly increasing the sensitivity of the instrument to adjacent organs. To minimize noise introduced in the sensor due to fluctuations in the applied field, the applied field is canceled at the position of the sensor. To overcome variations in the sensor output due to fluctuations in the applied field, change in the ambient temperature and mechanical relaxation of the instrument, the detector assembly is oscillated while the examined patient remains stationary.

Abstract: A Q-damping subsystem for either an NQR or NMR contraband detection receiver for effectively reducing the dead time and increasing sensitivity of the contraband detection system. The invention acts as an addition to the standard transmit circuits of NQR and NMR based scanners and spectrometers. The active Q-damping devices require additional circuitry for an NQR/NMR detection receiver and a programming for the control thereof. Typically, the detection receiver generates a high-voltage RF pulse on the order of 200-1000 V with normal operation of 100-300 microseconds in length to provide sufficient magnetic field characteristics to perturb the precessing nuclei. The NQR or NMR detection receiver electronics are very sensitive and have to detect a very weak nuclear induction pulse signal that is in the nano/micro-volt range.

Abstract: A probe instrument using room-temperature sensor(s) that can measure magnetic susceptibilities variations. The instrument has sufficient resolution to monitor paramagnetic materials in a human body, and preferably iron in a human liver by noninvasively examining patients with iron-overload diseases. The instrument includes room temperature magnetic sensors, and detects the sample, that is the tissue response to an alternating current field applied by an applied field coil. The sensors that can be used include magnetoresistive, fluxgate and magnetoinductive sensors. The applied field coil dimensions are chosen so that the applied field is optimized for maximum response from the liver while minimizing the effects due to the overlying abdominal tissue and at the same time not unduly increasing the sensitivity of the instrument to the lung. To minimize noise introduced in the sensor due to fluctuations in the applied field, the applied field is canceled at the position of the sensor, i.e.

Abstract: A system for detecting a target substance within a class of explosives and narcotics containing quadrupolar nuclei through the use of nuclear quadrupole resonance (NQR). The system applies an RF signal to a coil (34) to excite the substance under test. If the target material is present, an NQR signal will be picked up by the same coil, That signal is compared with known NQR signals in frequency and amplitude. A signal is displayed in an appropriate way if a threshold value of the NQR signal is equalled or exceeded. The empty coil is statically tuned by means of adjusting the location or capacitance values, or both, of static tuning capacitors (102) in the coil. The coil is tuned after the specimen is inserted into the coil by means of an auto-tune feature (36). Effective RFI shielding (37) is provided to prevent external contaminating signals from being detected by the coil and to prevent RF signals from escaping from the scanner. The invention also includes the method for performing tests with the system.

Abstract: Apparatus for tuning a system for detecting a target substance through the use of nuclear quadrupole resonance (NQR) or nuclear magnetic resonance (NMR). The apparatus tunes an RF coil (34) which is employed to excite the substance under test. The tuning apparatus (36) includes a series of fixed value capacitors (93) switched in the tuning circuit by controllable switches (94). A programmable controller (21) is employed to control the switching and thereby the tuning of the coil.

Abstract: A method and apparatus are disclosed for applying a low strength, time varying magnetic field to a selected screening region of a host, and for sensing a responsive magnetic field from a retained ferrous body within the screening region. The excitation field coil is designed to create a region of finite magnetic field within the screening region, and a region of near zero magnetic field. The sensors are placed within the region of near zero magnetic field to minimize the effect of the applied field. The effects of the applied field are further reduced by use of a reference sensor, field compensation coils, and a feedback loop. The magnetic gradient measured by the sensors is processed to locate and characterize the ferrous body.

Abstract: Apparatus for tuning a system for detecting a target substance through the use of nuclear quadrupole resonance (NQR) or nuclear magnetic resonance (NMR). The apparatus tunes an RF coil which is employed to excite the substance under test. The tuning apparatus includes a series of fixed value capacitors switched in the tuning circuit by controllable switches. A programmable controller is employed to control the switching and thereby the tuning of the coil.

Abstract: A system for detecting a target substance within a class of explosives and narcotics containing quadrupolar nuclei through the use of nuclear quadrupole resonance (NQR). The system applies an RF signal to a coil to excite the substance under test. If the target material is present, an NQR signal will be picked up by the same coil. That signal is compared with known NQR signals in frequency and amplitude. A signal is displayed in an appropriate way if a threshold value of the NQR signal is equalled or exceeded. The coil is tuned by means of an auto-tune feature. Effective RFI shielding is provided to prevent external contaminating signals from being detected by the coil and to prevent RF signals from escaping from the scanner. The invention also includes the method for performing tests with the system.

Abstract: A stochastic excitation, SQUID detection system for determining the frequency response of a sample. A pair of counterwound detection coils are adjacent to an excitation coil. The sample is selectively placed in one of the detection coils for taking measurements. The SQUID sensor is a broadband, high sensitivity device which enables the frequency response of the sample to be determined over a wide bandwidth with a single measurement.

Abstract: A thin film dc SQUID and its driving electronic circuitry configured with very high symmetry, having a SQUID loop formed with four holes (24, 24, 26, 27) at the respective ends of crossed slits (22, 23). Each of these holes forms a single turn secondary coil for symmetrically arranged pairs of modulation coils and signal coils. The geometrical placement of the modulation coils with respect to the signal coils results in a device which nominally has no mutual inductance between the two groups of coils when the SQUID is biased for normal operation. The external driving circuit (75-85) is configured to preserve the highly balanced nature of the SQUID and forces an equal magnitude of current to flow in all four of the bias leads.

Abstract: A method of bonding a superconductive ribbon lead to a superconductive bonding pad connected to superconducting circuitry. The thin ribbon is first coated with a fresh layer of the same material from which it is made and then a very thin layer of a noble metal is applied over that fresh layer. The bonding pad is also prepared with a very thin layer of the noble metal. Those coated surfaces are placed in facing contact and ultrasonically bonded.

Abstract: A method of bonding a superconductive ribbon lead to a superconducting bonding pad connected to superconducting circuitry. The thin ribbon is first coated with a fresh layer of the same material from which it is made and then a very thin layer of a noble metal is applied over that fresh layer. The bonding pad is also prepared with a very thin layer of the noble metal. Those coated surfaces are placed in facing contact and ultrasonically bonded.

Abstract: A thin film dc SQUID and its driving electronic circuitry configured with very high symmetry. The SQUID loop is formed with four holes at the respective ends of crossed slits. Each of these holes forms a single turn secondary for symmetrically arranged pairs of modulation coils and signal coils. The geometrical placement of the modulation coil transformers with respect to the signal coil transformers results in a device which nominally has no mutual inductance between the two groups of coils when the SQUID is biased for normal operation. The external driving circuit is configured to preserve the highly balanced nature of the chip and forces equal magnitudes of current to flow in all four of the bias leads.